can't give my gf an orgasm (or have I?)

right, basically when I lick her, she says that for a while it feels pleasurable, but then after too long, her leg starts to feel uncomfortable from it. So... what can I do to avoid that, any ideas?
Also she doesn't think she's ever had an actual orgasm, but sometimes I feel her vaginal muscles tightening around my fingers, is it possible this is an orgasm but she just doesn't recognise it? I mean I'd have thought she'd definitely know if she had one, but recently I found out she'd thought every time a girl orgasms, she ejaculates... when I told her that that wasn't true, she said stuff like "well maybe I have had one then, it does feel really good"

Hey m8, Rite basicly to me it sounds like she realy isnt comfterbul
try gettin her to relax her legs are feeling funny coz she is so tence,
i have had this prob a few times now an it is realy down to gettin her to relax get that an ur sorted,

Just make sure she aint tryin to sneek a cum haha!! to mean girls try tha one

She lays on her back, I kneel beside her and put my head between her legs and lick her clit, then fuck her pussy with my tongue then back to the clit, etc, till she pushes me away. No noise, no movement, she says she went off and I believe her. I would not know if I wasn't told except for pushing me away. I do not do it from below or even touch her legs in any way.

well I don't think they are tired, it's more to do with the nerves being affected by the licking, or something like that.
She might be uncomfortable perhaps, in that she says she feels unnatractive sometimes and she thinks about that, so maybe I just need to compliment her more hat

No, woman does not always "ejaculate". There are man yways to tell if a woman orgasms are not and the best description/demonstration I have found is in these videos http://www.welcomed.com/videos . I would tell you what they say but I don't think I could do it justice since they have like a 100 years of research on FEMALE ORGASM.